The present invention relates to a process for decreasing the time required for production of yogurt without compromise of product quality. More particularly, the invention relates to a process for decreasing the time required for yogurt production without compromise of quality by fermentation at about 105xc2x0 F. to about 115xc2x0 F. followed by direct acidification.
Over the last few years, yogurt and its preparations have developed into one of the most well-accepted and consumed fermented dairy products. A mildly acidic taste, good digestibility, variations in taste, and a high dietetic value have significantly contributed to this increased marketplace acceptance.
Yogurt is a firm, creamy or liquid acidified milk product which is manufactured from milk or a milk component by using thermophilic lactic acid bacteria. For increasing dry matter content, milk can be concentrated or powdered milk can be added during the production process. Exemplary of forms of yogurt are a gel-like form, stirred yogurt, and drinking yogurt in a liquid form.
The typical yogurt manufacturing process is depicted in FIG. 1. Basic yogurt manufacturing processes generally use a dairy medium such as milk or a milk component as starting material. The dairy medium is typically chosen from, but is not limited to, pasteurized or unpasteurized milk, cream, non-fat dried milk or concentrated milk and water. Other ingredients, such as various thickening agents/stabilizers (e.g., hydrocolloids such as starches or gelatins), and/or whey protein concentrates can optionally be added to adjust gel structure and/or consistency and the mixture is then heated to allow pasteurization and thickening. To this mixture is added yogurt-producing bacterial culture(s), and fermenting proceeds under heated conditions until the mixture reaches the required level of acidity to produce the yogurt. Fruit, flavorings, or colorants can optionally be added to the yogurt to produce the final commercial product.
During the yogurt production process, the rate limiting step is fermentation. Generally, the time period for the fermentation step is in the range of about two to about twelve hours, with most processes having fermentation steps that last approximately two to four hours. The present invention provides a new process by which the time necessary for this rate limiting fermentation step can be greatly decreased while producing a yogurt product with no compromise of quality (i.e. beneficial flavor, texture and other organoleptic qualities).
With respect to the dairy medium used in typical yogurt producing processes, certain percentages of fat and dry matter are chosen depending upon the final product desired. In order to obtain the desired gel structure in the yogurt with the desired consistency, the natural nonfat dry matter content can be adjusted by either addition of dry matter or by proper selection of the dairy medium starting material. For example, low-fat or skim milk yogurt has a softer gel than a whole milk yogurt; therefore, the dry matter content can be raised by addition of dry matter such as milk concentrate or milk powder or by water removal through evaporation.
Typically, optional ingredients are added to the dairy medium to adjust gel properties. For example, a typical process would use a starting mixture containing whey protein concentrate in the range of 0 to about 2%, a starch component in the range of 0 to about 5%, a sweetener in the range of 0 about 20%, a gelatin component in the range of 0 to about 3%, with the remainder of the mixture being the dairy medium (e.g., milk or milk components).
Once the dairy medium has been chosen, and optional ingredients desired are added, the mixture is generally heated to cause pasteurization and to denature whey protein. This pasteurization and thickening is generally accomplished by heating the mixture to about 180xc2x0 F. to about 200xc2x0 F. for about 2 to about 12 minutes, typically about 6 to about 9 minutes. After this heating step, the mixture is typically allowed to cool to about 105xc2x0 F. to about 115xc2x0 F. and placed into a fermentation tank wherein the temperature is continually maintained within the range of about 105xc2x0 F. to about 115xc2x0 F., yogurt culture is added and fermentation takes place until the mixture reaches appropriate levels of acidity. The acidification causes the coagulation of proteins that is responsible for the typical yogurt texture, and the typical yogurt flavor develops during acidification.
Starter cultures for yogurt generally are thermophilic (heat-loving) bacteria. Typical yogurt cultures are Streptococcus thermophilus and Lactobacillus bulgaricus. These bacteria are used in yogurt production because they can thrive and produce lactic acid at the temperatures used in conventional yogurt manufacturing. In the typical yogurt production process, fermentation proceeds until the pH of the mixture is below approximately 4.6. Below a pH of about 4.6 the final product is considered a high acid food and the product will not support growth of pathogenic bacteria. As previously described, this fermentation step is lengthy, usually requiring between 2 and 12 hours, more typically between 2 and 4 hours.
In typical yogurt producing processes, after the lengthy fermentation process has passed and the pH level has reached approximately 4.6, the mixture is cooled to about 35xc2x0 F. to about 45xc2x0 F., typically about 40xc2x0 F., resulting in the final yogurt product. The yogurt is sent to a storage tank, and from the storage tank the yogurt is sent to be packaged for sale. Other components, such as fruit, flavoring, coloring or sweetener can optionally be added previous to storage, during storage, or between storage and packaging.
As previously described, the rate limiting step in yogurt production is the fermentation step. As such, considerable expense is accrued in this step of the production process. Faster fermentation processes are necessary to increase production plant capacity and to create cost savings during the manufacturing process. The present invention relates to a process whereby the time required for the fermentation step is greatly reduced. More specifically, the present invention relates to an acidification process that greatly decreases the fermentation time, often by as much as 50%. This process can be used in the production of any dairy fermented product such as yogurt.
In one embodiment of the invention, a process for the production of a yogurt food product using reduced fermentation time without compromise of product quality is provided. The process comprises the steps of heating a yogurt ingredient composition for about 2 minutes to about 12 minutes at a temperature of about 180xc2x0 F. to about 200xc2x0 F., cooling the yogurt composition to a temperature of about 105xc2x0 F. to about 115xc2x0 F., adding a bacterial culture to the yogurt composition, fermenting the yogurt composition at a temperature of about 105xc2x0 F. to about 115xc2x0 F. until the pH of the composition reaches about 4.8 to about 5.2, adding a food grade acid directly to the yogurt composition to reduce the pH to about 4.6 or less, and cooling the yogurt composition rapidly to a temperature of about 45xc2x0 F. or lower. Thus, the acid may be added before or after cooling begins.
In another embodiment of the invention, a food grade acid is added directly to the yogurt composition to reduce the pH to about 4.6 or less, and then the yogurt composition is cooled rapidly to a temperature of about 45xc2x0 F. or lower. Accordingly, the acid is added after cooling begins.
In yet another embodiment of the invention, the food grade acid is added at a temperature of about 105xc2x0 F. to about 115xc2x0 F. at the time of direct acidification. Subsequently, the yogurt composition is cooled rapidly to a temperature of about 45xc2x0 F. or lower.
In any of the above-described embodiments of the invention the food grade acid may be any food grade acid known in the art, for example, the acid can be selected from the group consisting of food grade citric acid, lactic acid, malic acid, gamma delta lactone, tartartic acid, and combinations thereof. The bacteria used for fermentation of the yogurt composition may be any bacteria culture known in the art of yogurt production. Exemplary of such bacteria are Streptococcus thermophilus and Lactobacillus bulgaricus.